It’s rare that a show’s success can be calculated partly in cringes. But the discomfort that the Old Globe musical “The Scottsboro Boys” inspires is less a test of audience fortitude than a testament to the work’s artistic impact.

“Scottsboro,” based on a real-life legal travesty visited on nine black youths in 1930s Alabama, dares you to laugh at some of the most painfully clichéd portrayals of African-Americans outside of a Stepin Fetchit routine.

Not laugh at these conventions borrowed from the old minstrel shows, exactly. But find amused amazement at the reminders of how white America once preferred to view black people.

The musical, the final collaboration of composer John Kander and the late lyricist Fred Ebb – the great team behind “Cabaret” and “Chicago” – manages to be both funny and deeply unsettling, typically in the same moment.

Susan Stroman (“The Producers,” “Contact”), who directed and choreographed the controversial Broadway production, stages the West Coast premiere at the Globe with a versatile and committed 13-member cast that’s tuned into the piece’s sense of the audacious.

Their performances and the work of music director and conductor Eric Ebbenga’s nine-member orchestra (plus Jon Weston’s involving sounds design) bring pizazz to the show’s old-timey jazz and blues tunes, tap exhibitions and over-the-top comedy.

But always just below the surface, in the script by “Chicago” adapter David Thompson, is the sense of how ridicule, even in the name of entertainment, can act as a dehumanizing force. Although the blackface, shuck-and-jive minstrel tradition had mostly faded by the time the Scottsboro Boys were jailed in Alabama, its use in the musical to frame their story speaks to an atmosphere that allowed prejudice to fester.

The fact that all the vaudeville jollity, bug-eyed mugging and riotous costumes (by Toni-Leslie James) in “Scottsboro” is juxtaposed with scenes of real suffering and the specter of the electric chair makes for a contrast whose intimations are impossible to shake.

Although they came to be known by one label, the Scottsboro Boys actually didn’t know each other when they were jailed in 1931, accused of raping two white women while riding the rails through Jackson County. Death sentences and endless trials ensued, the wheels of Southern justice unimpeded even by the recantation of one accuser and intervention by the U.S. Supreme Court.

Their story, though, is introduced as just another lark of a tale to be told by the minstrel troupe, hosted by the Interlocutor (a perfectly avuncular and pompous Ron Holgate) with an assist from the gag-loving Mr. Bones (Jared Joseph) and Mr. Tambo (JC Montgomery).

Those actors and most of the others double and triple as additional characters, from cops to preachers to the defendants’ sympathetic but manipulative Northern lawyer, Samuel Leibowitz.